The electronic properties of van der Waals heterostructures composed of MoS2 and WS2 under a perpendicular electric field are studied in terms of field strength, electron doping concentration, and interlayer stacking arrangement based on the density-functional theory. The calculation results show that accumulated carrier distribution can be controlled by tuning the field direction, field strength, and doping concentration. The electron is localized on the MoS2 layer on the positively charged electrode side under a strong positive field with a low doping concentration, whereas they are extended throughout both the MoS2 and WS2 layers under a strong negative field. Stacking misorientation between the layers further enhances the electron localization under a positive field and delocalization under a strong negative field. The stacking arrangement and electric field allow additional tuning of the electronic properties of van der Waals heterostructures.